1. Field of the Invention
The present invention relates to a seat lock mechanism such as, for example, a vehicle seat lock mechanism for locking a seat slide unit on which a vehicle seat is mounted or a seat reclining unit mounted on the vehicle seat.
2. Description of Related Art
As a conventional seat slide unit, Japanese Patent Publication (examined) No. 62-61462 discloses a seat slide adjuster capable of adjusting the position of a seat step by step. This adjuster is intended to slide the seat by alternately engaging two lock plates with a plurality of latches of a latch plate. During a seat sliding operation, one of the lock plates is engaged with any one of the plurality of latches at all times.
Japanese Utility Model Publication (examined) No. 62-42834 discloses a seat slide unit for locking a seat by utilizing an inertial force. The seat slide unit is implemented by two independent lock portions disposed on respective sides of the seat. One of the lock portions is of a manual locking type for use in a normal seat sliding operation, while the other is of an inertial locking type for automatically locking the seat when an abrupt deceleration or acceleration is generated due to a vehicle collision or the like.
Japanese Utility Model Publication (examined) No. 63-46258 discloses a lock unit for locking a seat slide unit, wherein inclined surfaces are formed forwardly and rearwardly of a lock hole, thereby allowing a lock plate to be easily introduced into the lock hole.
On the other hand, a conventional seat reclining unit is intended to properly adjust the angle of inclination of a seat back generally by manually releasing engagement of a lock gear with a sector gear fixed to a seat back frame or by electrically swinging the sector gear.
Of the above-described conventional seat slide units, the seat slide adjuster disclosed in Japanese Patent Publication No. 62-61462 is required to move the seat by operating an operating lever pitch by pitch, resulting in a troublesome operation of the operating lever and much time required for moving the seat.
The seat slide unit disclosed in Japanese Utility Model Publication No. 62-42834 is of a structure in which the lock plate is immediately locked by an operation of a deceleration/acceleration sensor. This sensor is, however, ineffective when the lock lever is being operated.
The lock unit disclosed in Japanese Utility Model Publication No. 63-46258 does not guarantee that the lock plate be positively introduced into the lock hole along an inclined surface when deceleration or acceleration is applied to the seat while the position of the seat is being adjusted.
On the other hand, particularly in the manually-operated one of the seat reclining units, the seat back has been abruptly tilted forwards or backwards when deceleration or acceleration is applied to the seat during operation of the operating lever.